package org.langqiao.io.file;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Properties;

public class ReadConfigFile {
 
	 //根据key读取value
	 public static String readValue(String filePath,String key) {
		 Properties props = new Properties();
	     try {
	    	 InputStream in = new BufferedInputStream (new FileInputStream(filePath));
	    	 props.load(in);
	    	 String value = props.getProperty (key);
	    	 System.out.println(key+value);
	    	 return value;
	      } catch (Exception e) {
	    	 e.printStackTrace();
	    	 return null;
	      }
	 }
 
	 //读取properties的全部信息
	 public static void readProperties(String filePath) {
		 Properties props = new Properties();
		 try {
			 InputStream in = new BufferedInputStream (new FileInputStream(filePath));
			 props.load(in);
			 Enumeration en = props.propertyNames();
             while (en.hasMoreElements()) {
            	 String key = (String) en.nextElement();
            	 String Property = props.getProperty (key);
            	 System.out.println(key+Property);
             }
		 } catch (Exception e) {
			 e.printStackTrace();
		 }
	 }

    //写入properties信息
    public static void writeProperties(String filePath,String parameterName,String parameterValue) {
    	Properties prop = new Properties();
    	try {
    		InputStream fis = new FileInputStream(filePath);
            //从输入流中读取属性列表（键和元素对）
            prop.load(fis);
            //调用 Hashtable 的方法 put。使用 getProperty 方法提供并行性。
            //强制要求为属性的键和值使用字符串。返回值是 Hashtable 调用 put 的结果。
            OutputStream fos = new FileOutputStream(filePath);
            prop.setProperty(parameterName, parameterValue);
            //以适合使用 load 方法加载到 Properties 表中的格式，
            //将此 Properties 表中的属性列表（键和元素对）写入输出流
            prop.store(fos, "Update '" + parameterName + "' value");
        } catch (IOException e) {
        	System.err.println("Visit "+filePath+" for updating "+parameterName+" value error");
        }
    }

    public static void main(String[] args) {
    	readValue("info.properties","url");
        writeProperties("info.properties","age","21");
        readProperties("info.properties" );
        System.out.println("OK");
    }
}
